1. Field of the Invention
The invention relates to a curved conveyor with a toothed, endless belt and a guide for preventing radial migration of the belt.
2. Description of the Related Art
Conveyors are well-known apparatuses with belts for moving objects from one location to another and can comprise straight sections and curved sections. In curved conveyors, the speed of the belt inside edge (i.e., the smaller radius edge) is slower than the speed of the belt outside edge (i.e., the larger radius edge).
Some types of belts comprise multiple interlocking panels or modules that can compensate for this difference in speed by moving relative one another. For example, interlocking panels, such as those often utilized in baggage claim conveyors in airports, can overlap one another at the belt inside edge as the belt moves around the curved section of the conveyor. Modular belts comprise interlocking modules that can slide or otherwise move relative to one another to effectively alter the spacing between modules. As the modular belt moves around the curve, the spacing between the modules at the inside edge of the belt decreases while the spacing between the modules increases at the outside edge of the belt. A chain belt behaves similarly to the modular belt, except that links in the chain belt can move relative to one another. Tension on the belt in the curve tends to force the belt radially inward, thereby causing the belt to migrate inward while moving along the curved conveyor. A rigid belt, such as found in interlocking panels, tends to inherently resist inward migration, and additional resistance to migration is typically provided by a guide on the inside radius. Resistance to inward migration for a chain belt is provided by the sprockets' engagement with the chain links.
While the above conveyor belts compensate for the turn radius in a curved conveyor belt and offer some solutions to the problem of inward migration, they are not optimal for use in certain industries, such as the food industry. In the food industry, hygiene and cleanliness are critical, and fluids and debris can become lodged in the joints of the interconnecting panels, links, chains, and the like and are difficult to sanitarily remove. Endless thermoplastic belts having a generally continuous, smooth upper surface are preferred for use in the food industry.
One type of conveyor with an endless belt comprises a tensioned flat belt having smooth upper and lower surfaces and extending between a drive pulley and a tail piece (typically a pulley or a fixed bar). Friction between the drive pulley and the belt enables transfer of torque from the former to the latter to thereby induce movement of the belt.
The friction driven endless belt has the desired smooth upper surface, but the aforementioned problems associated with radial migration in a curved conveyor still exist. Prior art solutions for overcoming the radial inward force include guiding or tracking devices that support an outside edge of the belt and counteract the inward force. These devices are positioned along the curve and are located radially outwardly of the belt, such as along the edge of the belt.
Although these guiding devices function to prevent radial migration of the belt, friction driven endless belts are still not optimal for industries such as the food industry. Because tension on the belt is required to maintain the requisite friction for moving the belt, this type of conveyor does not performs well in environments where the tension and friction can be compromised. In the food industry, introduction of grease and effluents from food products can result in a loss of friction and thereby detrimentally affect the performance of the conveyor.
Alternatively, another conveyor with an endless belt comprises a low friction, direct drive belt having a flat upper surface and teeth-on a lower surface. This type of conveyor has the seamless flat upper surface that is easy to clean and overcomes the tension and friction problems associated with the friction driven flat belts. The teeth engage sheaves on a drive sprocket to transfer torque to the belt without requiring friction between the belt and the drive sprocket or tension in the belt. Such a conveyor is disclosed in U.S. Patent Application No. 60/593,493, which is incorporated herein by reference in its entirety. However, some radial migration of the low tension, direct drive belt remains an issue.